Mixing tanks with rotating agitator apparatus are typically used to mix chemical compounds. Frequently, the ingredients being mixed in the agitator tanks require a sterile environment prior to use and/or during use, such as when ingredients are being mixed to prepare a pharmaceutical product. To provide such a sterile environment, mixing vessels must be constructed to prevent contaminants from entering the vessel during the entire batch process, including filling the vessel, mixing the contents and draining the vessel.
Recently, sterile mixing tanks have been developed that utilize a flexible vessel, generally in the form of a plastic bag, as the mixing container. The flexible vessel can be constructed in a sterile environment and sealed prior to use. Flexible vessels may also be constructed, assembled and sealed in non-sterile manufacturing environments such as clean rooms prior to sterilization by gamma irradiation. Such systems, which use a tank support to maintain the integrity of the flexible container when filled, generally are disposed of after use, to obviate the need for cleaning so as to recreate a sterile environment in the vessel quickly between uses and eliminate the possibility of cross contamination.
To assist in maintaining a sterile environment, disposable mixing vessels have been manufactured with the agitator apparatus contained within the sealed vessel when shipped. In these mixing vessels, the agitator apparatus is placed within the vessel prior to sealing and subsequent sterilization by gamma irradiation so as to minimize the potential for breaching the sterile environment. To further reduce the chance of a breach of the sterile environment within the mixing vessel, these mixing vessels often employ magnetic drive means for driving the impellers, thus obviating the need for a physical connection through the vessel wall.
Examples of disposable mixing vessels with internally mounted impellers include U.S. Patent Publication Nos. 2005/0272146, 2006/0131765, 2005/0117449, 2007/0252290 and 2006/0092761. Each of these references describes a mixing vessel designed for a single or limited use with internal agitating apparatus including impellers that are activated by cooperating drive elements associated with a drive means.
The agitator apparatus of the prior art, however, generally use impellers that are formed in fixed relation to the structure on which they reside. As such, the minimum volume that a mixing vessel containing the agitator apparatus can be folded down to for shipping and storage is limited by the volume of space occupied by the agitator apparatus with fixed impellers. Additionally, fixed impellers are known to cause damage to the material of disposable, flexible mixing vessels due to high contact pressure over the small contact area of the impellers when the flexible mixing vessel with the agitator apparatus pre-fitted therein is packaged, shipped and/or stored.
It is therefore an object of the invention to provide a space saving agitator apparatus for a mixing vessel, to aid in the packing, shipping and storage of the agitator apparatus alone or pre-fitted into a flexible mixing vessel, such as a disposable, single use mixing vessel.
It is a further object of the invention to provide an agitator apparatus for a flexible mixing vessel where the impeller is less likely to damage the mixing vessel when the agitator apparatus comes into contact with the material of the mixing vessel.
It is another object of the invention to provide an agitator apparatus for a flexible mixing vessel with larger fins to increase mixing efficiency or permit the mixing of viscous materials without adding to the size of the flexible mixing vessel for packaging, shipping and/or storage.
It is still another object of the present invention to provide an agitator apparatus for a mixing vessel that can be quickly and easily made functional for mixing without breaching the sterile environment of a mixing vessel containing the agitator apparatus.